In the field of X-ray image diagnosis, X-ray diagnosis systems including a plurality of image acquisition apparatuses have been used. Such an X-ray diagnosis system includes a first image acquisition apparatus and a second image acquisition apparatus, for example. The first image acquisition apparatus is, for example, an X-ray television. The X-ray television is used in gastrointestinal series, urography, myelography, or cholangiography, for example. To acquire an X-ray image at an appropriate timing by enabling a rotation of anode quickly, the first image acquisition apparatus is sometimes provided with a first X-ray tube having an anode driven by a three-phase alternating current. By contrast, the second image acquisition apparatus is a general X-ray image acquisition apparatus, for example. The second image acquisition apparatus is provided with a second X-ray tube having an anode driven by a two-phase alternating current because the second image acquisition apparatus has a longer time allowance for enabling rotation of anode, compared with that in the first image acquisition apparatus.
Therefore, an anode-rotating coil driver capable of driving both the first X-ray tube and the second X-ray tube has been developed. The first X-ray tube is connected to the anode-rotating coil driver, and the anode-rotating coil driver drives the anode of the first X-ray tube in rotation. The second X-ray tube is also connected to the anode-rotating coil driver, and the anode-rotating coil driver drives the anode of the second X-ray tube in rotation. To drive the first X-ray tube, for example, the anode-rotating coil driver controls a three-phase inverter in such a manner that a three-phase alternating current with a phase difference of 120 degrees is supplied. To drive the second X-ray tube, the anode-rotating coil driver controls the three-phase inverter in such a manner that a two-phase alternating current with a phase difference of 90 degrees is supplied. Such an anode-rotating coil driver, however, may cause an arm short circuit when supplied is a two-phase alternating current.
To prevent two coils provided to the second X-ray tube from being applied with a voltage simultaneously, there has been an anode-rotating coil driver that brings the width of a voltage pulse applied to the coils to one fourth or less of the cycle of the alternating current voltage to be output. However, such an anode-rotating coil driver sometimes requires a long time for enabling rotation of anode, because the effective voltage of the alternating current applied to the coils is low.
There is another anode-rotating coil driver that is provided with two inverters, and an isolation transformer inserted between the first X-ray tube or the second X-ray tube and each of the inverters. Any arm short circuit does not occur in this anode-rotating coil driver. However, because this anode-rotating coil driver is provided with the isolation transformer, the weight and the size of the anode-rotating coil driver are increased disadvantageously.